1. Field of the Invention
The invention relates to a process for micronizing solid matter in jet mills, wherein the solid matter is brought into the jet mill across an injector by means of a propellant and wherein the micronizing takes place if necessary in the presence of grinding and/or dispersing agents.
2. Background of Information
The micronizing of solid matter can be carried out in jet mills, for example, of the type of the spiral or counter-pipe jet mills (CF Winnacker, Kuchler: Chemische Technologie, 4 Edition, Volume 1, P.91-93, Carl Hanser Verlag Munchen, Wien 1984). Jet mills consist of a milling section, into which water vapor jets or air jets are blown at high speeds, and the solid matter to be micronized (in the following also termed "milling goods") is brought in across an injector by a propellant. Compressed air or water vapor (in the following referred to in short as "steam"), is usually used as the propellant in this process. The introduction of the solid matter into the injector occurs as a rule across a feeding hopper or an entry chute.
Milling aids are also often added to the solid matter in order to support the micronization. Further, dispersing agents are usually used especially with pigments, improving their dispersability in various material and simultaneously supporting the micronizing of the pigment. The manner mentioned above of introducing solid matter into jet mills has the disadvantage that milling disturbances can occur as a result of blockages of the injector and sedimenting of the milling goods on the walls of the feeding hopper.
These milling disturbances lead as a rule to a decreased quality of the micronized solid matter. In addition, milling goods can leave the jet mill, which is at high pressure, during these milling disturbances.